Potassium Bromate vs Butylated Hydroxytoluene: which is worse?

What is Potassium Bromate?

Potassium bromate (KBrO3) is an oxidizing agent used in commercial bread baking as a flour maturing agent and dough conditioner. It strengthens gluten networks, improves dough elasticity, and produces a more uniform, light-textured baked product. It is a white crystalline powder.

What is Butylated Hydroxytoluene?

Butylated hydroxytoluene (BHT) is a synthetic phenolic antioxidant preservative derived from petroleum. A white crystalline solid with formula C15H24O, it prevents fat oxidation in processed foods, cosmetics, and industrial applications. Often used synergistically with BHA.

Documented risks

Potassium Bromate: Potassium bromate is classified by the International Agency for Research on Cancer (IARC) as Group 2B — a possible human carcinogen — based on sufficient evidence in animals. This classification was formalized in 1999. The landmark toxicology study is Kurokawa et al. (1990), published in Environmental Health Perspectives (PMC1567851), which demonstrated that KBrO3 induces renal cell tumors (kidney cancer), mesotheliomas of the peritoneum, and follicular cell tumors of the thyroid in rats. Importantly, the researchers demonstrated KBrO3 is a complete carcinogen — it possesses both tumor-initiating and tumor-promoting activities for renal tumorigenesis. The mechanism of carcinogenicity involves generation of reactive oxygen species, particularly hydroxyl radicals and superoxide radicals. These radicals cause oxidative DNA damage, specifically 8-hydroxydeoxyguanosine (8-OHdG) formation in rat kidney cells — a well-characterized biomarker of oxidative DNA damage. California declared potassium bromate a known carcinogen under Proposition 65 in 1991, requiring cancer warning labels on California products containing it. Multiple advocacy organizations including CSPI (1999 petition) and EWG (2015 petition) have petitioned the FDA for a federal ban. As of 2025, the FDA has urged voluntary industry elimination since the early 1990s but has not issued a formal ban. Nephrotoxicity from high-dose potassium bromate is well documented in case reports of accidental or intentional poisonings: it causes irreversible renal tubular necrosis, permanent deafness (cochlear damage), and blindness (optic nerve damage). These effects occur at doses far above food consumption scenarios but demonstrate the compound's acute toxicological potency. FDA testing in 1999 found residual potassium bromate above expert-recommended safe limits in more than half of 17 tested bread and roll products, demonstrating that the 'it bakes off completely' argument does not always hold in commercial practice.

Butylated Hydroxytoluene: BHT has complex, bidirectional carcinogenicity data — some NTP bioassays found liver tumors in female mice at high doses, while other studies suggested BHT might inhibit cancer initiation. IARC has not formally classified BHT due to conflicting evidence. A 2017 study linked BHT to thyroid hormone disruption in female rats. The American Academy of Pediatrics (2018) recommended reducing synthetic preservative exposure including BHT in children. Kellogg's uses vitamin E in European versions of cereals that contain BHT in US versions — a commercially meaningful substitution.